1. Field of the Invention
This invention relates generally to a method and apparatus for collecting, detecting and indicating true alveolar breath samples from humans and, in particular, is directed to an uncomplicated, user-friendly and relatively inexpensive apparatus and method for collecting such breath samples and detecting, indicating and thereby assuring that they consist primarily of alveolar gas as expelled from the pockets of the lungs.
1. Description of the Prior Art
Certain diagnostic techniques require analysis of the breath of a human subject to determine whether the breath contains a particular chemical compound, such as ethyl alcohol, carbon dioxide or ammonia, or a non-chemical, such as a particular microorganism. Determining the constituent components of the breath is best accomplished by analyzing the alveolar gas, that is the portion of the exhaled breath which is expelled from the air pockets of the lungs. In exhalation, as the lungs contract, breath contained in the mouth, throat and bronchials is necessarily exhaled first, followed by the breath contained in the alveoli of the lungs. Since it is at the alveoli where the exchange of substances between breath and blood ultimately occurs, the concentration of gaseous or vaporous constituents in the alveoli corresponds more closely to the concentration of substances dissolved in the blood. Thus, if a sample of breath is to be analyzed for the presence of constituents which may be present in the blood, the sample of breath analyzed must be at least primarily alveolar gas.
In order to make sure that a subject has expelled a full alveolar breath sample suitable for purposes of analysis, the apparatus and methods of the prior art utilize multiple collector configurations, with the alveolar portion of the expelled breath being collected in a second container. After collection of the alveolar portion of the breath sample in the second container, the alveolar breath present in the second container is then removed by means of a syringe and transferred in an evacuated tube. Such prior art techniques are awkward, difficult to use and risk prone (e.g., the syringes can be tempting to drug addicts).
More specifically, the equipment commonly used for collecting alveolar breath samples consists of bags, valves, syringe and needles and evacuated containers such as used for blood samples. These devices are expensive and complex which makes them very difficult for a patient to use. For example, U.S. Pat. No. 3,734,692 discloses an alveolar breath sampling apparatus utilizing a complicated compartmentalized bag having first and second inflatable regions. A dual channeled delivery port is constructed into the apparatus and communicates with both regions. The breath sample is collected by breathing into the delivery port resulting in the sequential collection in each region. This device is unnecessarily complex and expensive to construct.
In another known arrangement, the alveolar air portion of a person's breath is separated in response to the temperature of the conveyed air. For example, U.S. Pat. No. 4,248,245 discloses a method and device for separating alveolar air which includes conveying the exhaled air through a conduit and continuously monitoring the temperature of the conveyed air. When the variation in measured temperature drops below a threshold value, the air is directed into a measuring chamber. This device is also excessively complex and expensive to manufacture.
In still another prior art arrangement, two separate collection bags are used interconnected by a conduit. For example, in U.S. Pat. No. 3,544,273, a first collection bag and a second collection bag are connected by a T-shaped conduit having one branch formed into a mouth piece. The breath sample is collected by inflating the first bag with the initial breath portion and filling the second bag will the alveolar air. The second bag is sealed by using a valve structure. The complexity of these devices and resultant difficulty individual users have in operating them and the absence of a positive means for detecting and indicating the presence of a full alveolar breath sample have often resulted in less than accurate measurements. In addition, such prior art systems are intimidating to the user and difficult to use in any event and thus are not as widely used as considered medically prudent for early diagnostic purposes.
In addition, because of the high cost of such prior art apparatus, the economics of use often dictate that the apparatus be reused instead of being discarded after initial use. It is a common practice, therefore, to sterilize and reuse such apparatus for other patients after each use. Because sterilization may not always be fully effective and because contamination of the apparatus may occur in any event prior to the next use, patients subsequently using the apparatus are exposed to additional risks.